The present invention relates to expandible devices for internally gripping cores or the like.
In conventional web treatments, where machines handle reels of paper, plastics, metal foils, textiles and other sheet material, the cores of these reels need to be mounted on the machines so that rotational drive can be selectively coupled to the cores to effect winding or unwinding of the web entrained on the cores. The cores carrying the webs are normally tubular components made from cardboard, metal or plastics material. To effect the rotational drive to a core, it is well known to employ an expandible device or core chuck onto which the core is mounted. The device then expands when it is desired to drive or lock the core to frictionally grip the interior of the core. Examples of known devices are described in U.K. patent specification Nos. 1,301,658, 1,362,649, 1,485,031 and 1,543,571. The known devices suffer from a number of disadvantages. Primarily:
(I) The range of expansion is often limited so that a particular device may need to be adopted for specific sizes of cores;
(II) There is often a relatively small zone of frictional contact between the interior of the core and the device when the latter is expanded to grip the core;
(III) In order to produce a compact device hitherto, the strength of certain components has to be sacrificed; and
(IV) Positive location of individual parts of the devices is often difficult to achieve.
A general object of the present invention is to provide an improved form of expandible device for internally gripping cores or the like.